Ligang Yuan

A Cs₄PbI₆‐mediated method is developed to fabricate cesium (Cs)‐rich perovskite films. It is also found that ≈15% alloying with the organic formamidine (FA) cation can sufficiently stabilize the perovskite phase with excellent phase and UV‐irradiation stability. FA_0.15Cs_0.85PbI₃‐based perovskite solar cells achieve a champion power conversion efficiency of 17.5%.

Abstract

The stability issue is still one of the main limitations of the commercialization of perovskite photovoltaics. The mixed cation FA _x Cs_{1 −x} PbI₃ has shown great promise owing to its improved thermal and moisture stability. However, the study of FA _x Cs_{1 −x} PbI₃ is concentrated on formamidine (FA)‐rich perovskite, whereas cesium (Cs)‐rich FA _x Cs_{1 −x} PbI₃ perovskites are barely studied due to the inevitable phase separation when Cs > 30 mol%. Here, a Cs₄PbI₆‐mediated method is developed to synthesize Cs‐rich FA _x Cs_{1 −x} PbI₃ perovskites. It is demonstrated that Cs₄PbI₆ intermediate phase has a low Cs cation diffusion barrier and therefore offers a fast ion exchange with the preformed FA‐rich perovskite phase to finally form the Cs‐rich FA _x Cs_{1 −x} PbI₃ perovskite. The results indicate that ≈15% alloying with organic FA cations can sufficiently stabilize the perovskite phase with excellent phase and UV‐irradiation stability. The FA_0.15Cs_0.85PbI₃ perovskite solar cells achieve a champion power conversion efficiency of 17.5%, showing the great potential of Cs‐based perovskites for efficient and stable solar cells.

CsPbI₃ perovskite quantum dot (PQD) hybrid nonfullerene organic solar cells are fabricated. The devices based on a PTB7‐Th:FOIC blend with PQDs yield higher efficiency of 13.2% even at near‐zero driving force than that without PQDs (11.6%). Incorporation of PQDs also leads to efficiency enhancement from 15.4% to 16.6% for a PM6:Y6 blend.

Abstract

To take advantages of the intense absorption and fluorescence, high charge mobility, and high dielectric constant of CsPbI₃ perovskite quantum dots (PQDs), PQD hybrid nonfullerene organic solar cells (OSCs) are fabricated. Addition of PQDs leads to simultaneous enhancement of open‐circuit voltage (V _OC), short‐circuit current density (J _SC), and fill factor (FF); power conversion efficiencies are boosted from 11.6% to 13.2% for PTB7‐Th:FOIC blend and from 15.4% to 16.6% for PM6:Y6 blend. Incorporation of PQDs dramatically increases the energy of the charge transfer state, resulting in near‐zero driving force and improved V _OC. Interestingly, at near‐zero driving force, the PQD hybrid OSCs show more efficient charge generation than the control device without PQDs, contributing to enhanced J _SC, due to the formation of cascade band structure and increased molecular ordering. The strong fluorescence of the PQDs enhances the external quantum efficiency of the electroluminescence of the active layer, which can reduce nonradiative recombination voltage loss. The high dielectric constant of the PQDs screens the Coulombic interactions and reduces charge recombination, which is beneficial for increased FF. This work may open up wide applicability of perovskite quantum dots and an avenue toward high‐performance nonfullerene solar cells.

Poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)‐metal oxides have regulated wettability and work function and exhibit much higher performance in inverted perovskite solar cell. The best efficiency is based on PEDOT:PSS‐MoO _x , with power conversion efficiency up to 19.64% for CH₃NH₃PbI₃. Meanwhile, the PEDOT:PSS‐MoO _x device maintains an efficiency of over 90% and 80% through 45 d follow‐up in N₂ or 20 d in air, respectively.

Abstract

Poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) can be roll‐to‐roll deposited on the substrate facilely in the electronics, but its acidity and mismatched energy level limit the performance and stability. Herein, different metal salts are incorporated into PEDOT:PSS solution to prepare PEDOT:PSS‐A _x O _y (metal oxide) composite hole transport layer and it is found that the performance of inverted perovskite solar cells (PSCs) can be greatly enhanced. PSC using PEDOT:PSS‐MoO _x has achieved much higher power conversion efficiency (PCE) (19.64%) than that of pristine PEDOT:PSS (12.19%). Two key factors are important for the performance enhancement. First, the increased surface free energy of PEDOT:PSS‐A _x O _y is beneficial for the formation of large crystal size and pinhole‐free film, leading to reduced nonradiative recombination. Second, the work function of PEDOT:PSS can be tuned to match the energy level of photoactive layer with small amount incorporation, which greatly enhances the photovoltage by a factor of 1.1. Besides, the devices based on PEDOT:PSS‐A _x O _y exhibit improved long‐term stability. Unencapsulated PSCs with PEDOT:PSS‐MoO _x retain over 90% and 80% of their initial PCEs in N₂ for 45 d and in ambient air for 20 d, respectively. The modified PEDOT:PSS solutions overcome the intrinsic imperfection and can be potentially employed for large‐scale production in the electronic devices.

Inorganic and organic electron transport layers (ETLs) have become a popular choice as selective contact materials for perovskite solar cells (PSCs). Herein, an overview of various inorganic and organic ETLs synthesis, properties, and their application in PSCs for different architectures, etc., to achieve high power conversion efficiency and functional stability is provided.

The presence of the electron transport layer (ETL) in perovskite solar cells (PSCs) is critical due to the requirement of enhancing the electron collection selectivity. ETLs are essential for achieving a high open‐circuit voltage (V _OC), high fill factor (FF), better transport of directional charges, better absorption of incoming light, and thermodynamically competent operation of photogenerated carrier populations. ETLs are sorted as organic, inorganic, or mixed, with different stability, cost effect, and directional charge transport ability. For instance, by using metal oxides as ETLs, power conversion efficiencies (PCEs) higher than 23% are reached for PSCs. Despite the advantages of metal oxide–ETLs and other organic or mixed ETLs, some questions still have to be addressed to achieve better PCEs, like how to passivate or eliminate the surface traps, how to upgrade the comprehension of the heterointerface, and optimization of morphology. Herein, different considerations of ETLs in different physical and environmental conditions, and different deposition methods used, are presented. Finally, the current studies and future challenges are analyzed in the domain of highly efficient PSCs with various ETLs.

Disorderly conduct : A crystal‐engineering strategy has been introduced to narrow the band gap of benchmark double perovskite Cs₂AgBiBr₆. The band gap of Cs₂AgBiBr₆ crystals can be reduced from 1.98 eV to 1.72 eV, reaching the smallest reported band gap for Cs₂AgBiBr₆ under ambient conditions. DFT calculations indicate that Ag–Bi disorder in the crystal structure could lead to band‐gap narrowing.

Abstract

Environmentally friendly halide double perovskites with improved stability are regarded as a promising alternative to lead halide perovskites. The benchmark double perovskite, Cs₂AgBiBr₆, shows attractive optical and electronic features, making it promising for high‐efficiency optoelectronic devices. However, the large band gap limits its further applications, especially for photovoltaics. Herein, we develop a novel crystal‐engineering strategy to significantly decrease the band gap by approximately 0.26 eV, reaching the smallest reported band gap of 1.72 eV for Cs₂AgBiBr₆ under ambient conditions. The band‐gap narrowing is confirmed by both absorption and photoluminescence measurements. Our first‐principles calculations indicate that enhanced Ag–Bi disorder has a large impact on the band structure and decreases the band gap, providing a possible explanation of the observed band‐gap narrowing effect. This work provides new insights for achieving lead‐free double perovskites with suitable band gaps for optoelectronic applications.

Soft routed benzimidazole clubbed phenoxazine‐based organic ionic plastic crystals with iodide and bromide anions successfully introduced as hole transporting materials in perovskite solar cells yield power conversion efficiencies exceeding 18%, which represents the best alternative to existing spiro‐OMeTAD due to high conductivity and hole mobility with a safer, stable, and efficient system.

Abstract

Organic ionic plastic crystals (OIPCs) are synthesized through a simple metal‐free, cost‐effective approach. The strategized synchronization of electron‐rich phenoxazine with benzimidazolium iodide (OIPC‐I) and bromide (OIPC‐Br) salts lead to enhanced hole mobility and conductivity of OIPCs which is suitable for an efficient alternative to conventional organic hole transporting materials (HTMs) for stable perovskite solar cells (PSCs). The fabricated PSCs with OIPC‐I as hole transporting layer yielded a power conversion efficiency of 15.0% and 18.1% without and with additive (Li salt) respectively, which are comparable with spiro‐OMeTAD based devices prepared under similar conditions. Furthermore, the PSCs with OIPCs show good stability compared to the spiro‐OMeTAD with or without additives. Here, first time benzimidazolium‐based OIPCs have been used as an alternative organic HTM for perovskite solar cells, which opens a window for the design of effective OIPCs for highly efficient PSCs with long‐term stability.

In this comprehensive review, the main challenges and the current status of perovskite/silicon, perovskite/CIGS, and perovskite/perovskite tandem technologies are presented. A specific focus is set on advanced characterization methods as well as simulations being utilized for perovskite‐based tandem solar cells to overcome the challenges and gain deeper knowledge to further improve device performance. Finally, the efficiency potentials in different experimental and theoretical limits are compared and pathways toward 35% efficiency are outlined.

Abstract

Tandem solar cells are the next step in the photovoltaic (PV) evolution due to their higher power conversion efficiency (PCE) potential than currently dominating, but inherently limited, single‐junction solar cells. With the emergence of metal halide perovskite absorber materials, the fabrication of highly efficient tandem solar cells, at a reasonable cost, can significantly impact the future PV landscape. The perovskite‐based tandem solar cells have already shown that they can convert light more efficiently than their standalone sub‐cells. However, to reach PCEs over 30%, several challenges have to be overcome and the understanding of this fascinating technology has to be broadened. In this review, the main scientific and engineering challenges in the field are presented, alongside a discussion of the current status of three main perovskite tandem technologies: perovskite/silicon, perovskite/CIGS, and perovskite/perovskite tandem solar cells. A summary of the advanced structural, electrical, optical, radiative, and electronic characterization methods as well as simulations being utilized for perovskite‐based tandem solar cells is presented. The main findings are summarized and the strength of the techniques to overcome the challenges and gain deeper knowledge for further performance improvement is assessed. Finally, the PCE potential in different experimental and theoretical limits is compared with an aim to shed light on the path towards overcoming the 30% efficiency threshold for all of the three herein reviewed tandem technologies.

MABr induces the remarkably oriented growth of tin halide perovskite films (MA _x FA_{1− x} SnI_{3− x} Br _x ) by alloying, which results in an optimal device conversion efficiency of 9.31% enhanced from 5.02% of the pristine FASnI₃ device and maintained above 80% of the initial efficiency after 300 h light soaking while the control device fails within 120 h.

Abstract

As the most promising lead‐free branch, tin halide perovskites suffer from the severe oxidation from Sn²⁺ to Sn⁴⁺, which results in the unsatisfactory conversion efficiency far from what they deserve. In this work, by facile incorporation of methylammonium bromide in composition engineering, formamidinium and methylammonium mixed cations tin halide perovskite films with ultrahighly oriented crystallization are synthesized with the preferential facet of (001), and that oxidation is suppressed with obviously declined trap density. MA⁺ ions are responsible for that impressive orientation while Br^‐ ions account for their bandgap modulation. Depending on high quality of the optimal MA_0.25FA_0.75SnI_2.75Br_0.25 perovskite films, their device conversion efficiency surges to 9.31% in contrast to 5.02% of the control formamidinium tin triiodide perovskite (FASnI₃) device, along with almost eliminated hysteresis. That also results in the outstanding device stability, maintaining above 80% of the initial efficiency after 300 h of light soaking while the control FASnI₃ device fails within 120 h. This paper definitely paves a facile and effective way to develop high‐efficiency tin halide perovskites solar cells, optoelectronic devices, and beyond.

The incorporation of potassium can remarkably stabilize wide‐bandgap perovskites with a high Br content by the synergistic effect of the formation of 2D K₂PbI₄ at the grain boundaries and the interstitial occupancy in the perovskite lattices, which can effectively reduce the trap density and inhibit ion migration, thus suppressing the nonradiative recombination and photoinduced phase segregation.

Wide‐bandgap perovskites have great potential to enable high‐efficiency tandem photovoltaics by combining with the well‐established low‐bandgap absorbers. However, such wide‐bandgap perovskites are often necessarily constructed with a high Br content, and thus faced with issues of phase segregation–induced photoinstability and high defect density, severely hindering their photovoltaic performance. Herein, a remarkable boost of the stability and efficiency of wide‐bandgap perovskite solar cells (PSCs) is demonstrated by simply incorporating potassium ions. Experiments have shown the interstitial occupancy of potassium ions in the perovskite lattice and the formation of 2D K₂PbI₄ at the grain boundaries, both can reduce the trap density and inhibit ion migration, and thus suppress nonradiative recombination and photoinduced phase segregation. The average power conversion efficiency (PCE) of photovoltaic devices based on the perovskite with 40% Br is improved from 15.28% to 17.94%, among which the champion efficiency is 18.38% with an optimal 15% KI incorporation. Importantly, the champion open‐circuit voltage (V _oc) remains unchanged (≈1.25 V) even when the bandgap reduces from 1.80 to 1.75 eV due to KI doping, effectively reducing the V _oc deficit. In addition, the unencapsulated cells can sustain 94% of the initial PCE after 2000 h of storage in ambient atmosphere, affirming their outstanding stability.

A new spiro derivative, SPS‐4F, is designed and synthesized as a nonfullerene electron transport material in perovskite solar cells. An efficiency of 20.31% and high device stability are simultaneously achieved in the resultant devices. This work opens up opportunities to obtain a new family of spiro‐based electron transport materials and paves a way for realizing high‐performance devices with low cost.

Abstract

Electron transport materials (ETMs) play a significant role in perovskite solar cells (PSCs). However, conventional solution processable organic ETMs are mainly restricted to fullerene derivatives and it is challenging to obtain nonfullerene ETMs with satisfactory properties. In this work, a new organic semiconductor SPS‐4F is synthesized by utilizing the classical spiro[fluorine‐9′9‐thioxanthene] unit to construct a π‐extended core. Although spiro is normally used in hole transport materials, the new spiro derivative SPS‐4F is successfully used as an ETM in inverted PSCs with power conversion efficiency over 20%. In addition, SPS‐4F can strongly coordinate with MAPbI₃ perovskite and lead to efficient surface trap passivation. The resultant PSCs exhibit excellent stability in air because of the hydrophobic property of SPS‐4F. This work opens up opportunities to obtain a new family of ETMs based on spiro and paves a way to the fabrication of high‐performance PSCs with low cost.

High‐efficiency and stable dopant‐free poly(3‐hexylthiophene) (P3HT)‐based CsPbI₂Br solar cells are achieved by introducing an optimized preannealing process to engineer the nucleation and crystallization of CsPbI₂Br films. Further incorporation of an ultrathin wide‐bandgap diphenylamine derivative layer (poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co ‐(4,4′‐(N ‐(4‐sec‐butylphenyl)diphenylamine)]) to regulate the band alignment of CsPbI₂Br and P3HT delivers a record‐high efficiency of 15.50% for dopant‐free P3HT‐based CsPbI₂Br solar cells.

Abstract

CsPbI₂Br is emerging as a promising all‐inorganic material for perovskite solar cells (PSCs) due to its more stable lattice structure and moisture resistance compared to CsPbI₃, although its device performance is still much behind this counterpart. Herein, a preannealing process is developed and systematically investigated to achieve high‐quality CsPbI₂Br films by regulating the nucleation and crystallization of perovskite. The preannealing temperature and time are specifically optimized for a dopant‐free poly(3‐hexylthiophene) (P3HT)‐based device to target dopant‐induced drastic performance degradation for spiro‐OMeTAD‐based devices. The resulting P3HT‐based device exhibits comparable power conversion efficiency (PCE) to spiro‐OMeTAD‐based devices but much enhanced ambient stability with over 95% PCE after 1300 h. A diphenylamine derivative is introduced as a buffer layer to improve the energy‐level mismatch between CsPbI₂Br and P3HT. A record‐high PCE of 15.50% for dopant‐free P3HT‐based CsPbI₂Br PSCs is achieved by alleviating the open‐circuit voltage loss with the buffer layer. These results demonstrate that the preannealing processing together with a suitable buffer layer are applicable strategies for developing dopant‐free P3HT PSCs with high efficiency and stability.

Herein, a novel precursor (HCOOCs and HPbX₃) for deposition of high‐quality CsPbI₂Br films, irrespective of humidity is presented. CsPbI₂Br cells prepared in an atmosphere with 30% and 91% relative humidity exhibit efficiencies of 16.1% and 15.1%, respectively, which are the highest among all inorganic CsPbX₃ (X: I, Br, or mixed halides) PSCs prepared in a medium or high humid atmosphere.

Abstract

High temperature stable inorganic CsPbX₃ (X: I, Br, or mixed halides) perovskites with their bandgap tailored by tuning the halide composition offer promising opportunities in the design of ideal top cells for high‐efficiency tandem solar cells. Unfortunately, the current high‐efficiency CsPbX₃ perovskite solar cells (PSCs) are prepared in vacuum, a moisture‐free glovebox or other low‐humidity conditions due to their poor moisture stability. Herein, a new precursor system (HCOOCs, HPbI₃, and HPbBr₃) is developed to replace the traditional precursors (CsI, PbI₂, and PbBr₂) commonly used for solar cells of this type. Both the experiments and calculations reveal that a new complex (HCOOH•Cs⁺) is generated in this precursor system. The new complex is not only stable against aging in humid air ambient at 91% relative humidity, but also effectively slows the perovskite crystallization, making it possible to eliminate the popular antisolvent used in the perovskite CsPbI₂Br film deposition. The CsPbI₂Br PSCs based on the new precursor system achieve a champion efficiency of 16.14%, the highest for inorganic PSCs prepared in ambient air conditions. Meanwhile, high air stability is demonstrated for an unencapsulated CsPbI₂Br PSC with 92% of the original efficiency remaining after more than 800 h aging in ambient air.

Publication date: 20 May 2020

Source: Joule, Volume 4, Issue 5

Author(s): Yan Jiang, Shih-Chi Yang, Quentin Jeangros, Stefano Pisoni, Thierry Moser, Stephan Buecheler, Ayodhya N. Tiwari, Fan Fu

Recent progress in inorganic lead‐based and lead‐free CsBX₃ perovskite solar cells using various strategies is reviewed and their prospects and challenges in the future are discussed in detail.

Abstract

All‐inorganic perovskite semiconductors have recently drawn increasing attention owing to their outstanding thermal stability. Although all‐inorganic perovskite solar cells (PSCs) have achieved significant progress in recent years, they still fall behind their prototype organic–inorganic counterparts owing to severe energy losses. Therefore, there is considerable interest in further improving the performance of all‐inorganic PSCs by synergic optimization of perovskite films and device interfaces. This review article provides an overview of recent progress in inorganic PSCs in terms of lead‐based and lead‐free composition. The physical properties of all‐inorganic perovskite semiconductors as well as the hole/electron transporting materials are discussed to unveil the important role of composition engineering and interface modification. Finally, a discussion of the prospects and challenges for all‐inorganic PSCs in the near future is presented.

This review focuses on the usefulness of spatially resolved analysis of halide perovskite solar cells. Methods sensitive to open circuit voltage, short circuit current, fill factor, and cell efficiency are discussed, and the specific value of the spatial information is demonstrated in quantitative loss analyses.

Abstract

This review explores the current state of the art in spatially resolved characterization of mixed‐halide perovskite solar cells. As the size of perovskite cells and modules continues to grow, quantification of the spatial distribution of key cell parameters will become increasingly valuable in predicting ultimate cell‐level performance and tracking process homogeneity. Here, both high resolution microscopic approaches using scanning techniques and camera‐based methods for full‐area cell and/or module analysis are discussed. The value of this local data in predicting performance losses at the cell level is particularly emphasized. Measurable physical parameters sensitive to losses of voltage, current, fill factor, and efficiency are discussed together with selected experimental results. It is demonstrated that a combination of spatially resolved cell parameter mapping/imaging can be used to quantitatively discriminate various loss contributions at high resolution. The impact and control of inhomogeneities become particularly important when upscaling from small devices to large formats compatible with industrial mass production.

Lead‐free Cs₂AgBiCl₆ double perovskite films with balanced stoichiometry, compact morphology, and high crystallinity are fabricated by a sequential vapor deposition method. Their application is explored as an ultraviolet photodetector which realizes low dark current density (≈10⁻⁷ mA cm⁻²), high detectivity (≈10¹² Jones), and stability (4 months). This work reveals the potential of Cs₂AgBiCl₆ double perovskites in ultraviolet detection.

Abstract

Double perovskites have shown great potentials in addressing the toxicity and instability issues of lead halide perovskites toward practical applications. However, fabrication of high‐quality double perovskite thin films has remained challenging. Here, sequential vapor deposition is used to fabricate high‐quality Cs₂AgBiCl₆ perovskite films with balanced stoichiometry, superior morphology, and highly oriented crystallinity, with an indirect bandgap of 2.41 eV. Using a diode structure, self‐powered Cs₂AgBiCl₆ ultraviolet (UV) photodetectors are demonstrated with high selectivity centered at 370 nm, with low dark current density (≈10⁻⁷ mA cm⁻²), high photoresponsivity (≈10 mA W⁻¹), and detectivity (≈10¹² Jones). Its detectivity is among the highest in all double‐perovskite‐based photodetectors reported to date and surpassing the performance of other perovskite photodetectors as well as metal oxide in the UV range. The devices also show excellent environmental and irradiation stability comparable to state‐of‐the‐art UV detectors. The findings help pave the way toward application of double perovskites in optoelectronic devices.

Publication date: Available online 23 April 2020

Source: Joule

Author(s): Nicole Moody, Samuel Sesena, Dane W. deQuilettes, Benjia Dak Dou, Richard Swartwout, Joseph T. Buchman, Anna Johnson, Udochukwu Eze, Roberto Brenes, Matthew Johnston, Christy L. Haynes, Vladimir Bulović, Moungi G. Bawendi

The structure and formation mechanism of spin‐coated films of lead‐free Sn‐based Ruddlesden–Popper (Sn‐RDP) perovskites are unveiled by combining results from in situ grazing incidence wide‐angle X‐ray scattering measurements and other extensive ex situ characterization methods. The formation of films with oriented Sn‐RDP crystallites is the result of bulk crystallization suppression induced by the presence of the 2D component (PEA⁺) during the drying process.

Abstract

Knowledge of the mechanism of formation, orientation, and location of phases inside thin perovskite films is essential to optimize their optoelectronic properties. Among the most promising, low toxicity, lead‐free perovskites, the tin‐based ones are receiving much attention. Here, an extensive in situ and ex situ structural study is performed on the mechanism of crystallization from solution of 3D formamidinium tin iodide (FASnI₃), 2D phenylethylammonium tin iodide (PEA₂SnI₄), and hybrid PEA₂FA _{n −1}Sn _n I_{3 n +1} Ruddlesden–Popper perovskites. Addition of small amounts of low‐dimensional component promotes oriented 3D‐like crystallite growth in the top part of the film, together with an aligned quasi‐2D bottom‐rich phase. The sporadic bulk nucleation occurring in the pure 3D system is negligible in the pure 2D and in the hybrid systems with sufficiently high PEA content, where only surface crystallization occurs. Moreover, tin‐based perovskites form through a direct conversion of a disordered precursor phase without forming ordered solvated intermediates and thus without the need of thermal annealing steps. The findings are used to explain the device performances over a wide range of composition and shed light onto the mechanism of the formation of one of the most promising Sn‐based perovskites, providing opportunities to further improve the performances of these interesting Pb‐free materials.

Bi³⁺‐Ln³⁺ (Ln=Er, Yb) codoping imparts optical functionality to Cs₂AgInCl₆ double perovskite. Bi³⁺ tailors optical absorption, thereafter non‐radiatively exciting Er³⁺ or Yb³⁺ f‐electrons, which then de‐excite by emitting 1540 and 994 nm near‐infrared (NIR) light, respectively.

Abstract

Bi³⁺ and lanthanide ions have been codoped in metal oxides as optical sensitizers and emitters. But such codoping is not known in typical semiconductors such as Si, GaAs, and CdSe. Metal halide perovskite with coordination number 6 provides an opportunity to codope Bi³⁺ and lanthanide ions. Codoping of Bi³⁺ and Ln³⁺ (Ln=Er and Yb) in Cs₂AgInCl₆ double perovskite is presented. Bi³⁺‐Er³⁺ codoped Cs₂AgInCl₆ shows Er³⁺ f‐electron emission at 1540 nm (suitable for low‐loss optical communication). Bi³⁺ codoping decreases the excitation (absorption) energy, such that the samples can be excited with ca. 370 nm light. At that excitation, Bi³⁺‐Er³⁺ codoped Cs₂AgInCl₆ shows ca. 45 times higher emission intensity compared to the Er³⁺ doped Cs₂AgInCl₆. Similar results are also observed in Bi³⁺‐Yb³⁺ codoped sample emitting at 994 nm. A combination of temperature‐dependent (5.7 K to 423 K) photoluminescence and calculations is used to understand the optical sensitization and emission processes.