ZiQi Sun

Bond length and bond angle exhibited by valence electrons is essential to the core of chemistry. Using lead-based organic–inorganic perovskite compounds as an exploratory platform, it is demonstrated that the modulation of valence electrons by compression can lead to discovery of new properties of known compounds. Yet, despite its unprecedented progress, further efficiency boost of lead-based organic–inorganic perovskite solar cells is hampered by their wider bandgap than the optimum value according to the Shockley–Queisser limit. By modulating the valence electron wavefunction with modest hydraulic pressure up to 2.1 GPa, the optimized bandgap for single-junction solar cells in lead-based perovskites, for the first time, is achieved by narrowing the bandgap of formamidinium lead triiodide (HC(NH₂)₂PbI₃) from 1.489 to 1.337 eV. Strikingly, such bandgap narrowing is partially retained after the release of pressure to ambient, and the bandgap narrowing is also accompanied with double-prolonged carrier lifetime. With First-principles simulation, this work opens a new dimension in basic chemical understanding of structural photonics and electronics and paves an alternative pathway toward better photovoltaic materials-by-design.

Hydrostatic pressure is applied to precisely modulate the structural and optical properties of lead-based organic–inorganic hybrid perovskites in a clean and effective manner. The optimal Shockley–Queisser bandgap for a single junction solar cell has been unprecedentedly achieved in HC(NH₂)₂PbI₃ (FAPbI₃), and two benign phenomena are accompanied with the narrowed bandgap, including prolonged carrier lifetime and ambient retainability.

On page 8221, S. Lilliu and co-workers show how synchrotron nXRD can be used to simultaneously probe the morphology and the structural properties of spin-coated CH₃NH₃PbI₃ perovskite films for photovoltaic devices. A method to visualize, selectively isolate, and structurally characterize single perovskite grains buried within a complex, polycrystalline film is developed.

Acceptor alloys based on n-type small molecular and fullerene derivatives are used to fabricate the ternary solar cell. The highest performance of optimized ternary device is 10.4%, which is the highest efficiency for one donor/two acceptors-based ternary systems. Three important parameters, J_SC, V_OC, and FF, of the optimized ternary device are all higher than the binary reference devices.

Ambipolar perovskite field-effect transistors and inverters with balanced mobilities are demonstrated. Thin-film field-effect-transistor-like inverters are developed, and a maximum gain of 23 in the first quadrant for V_DD = 80 V is obtained.

The spin on a ferromagnetic Co surface can interact with the asymmetric orbital on an organometal halide perovskite surface, leading to an anisotropic magnetodielectric effect. This study presents an opportunity to integrate ferromagnetic and semiconducting properties through the Rasbha effect for achieving spin-dependent electronic functionalities based on thin-film design.

A novel-small molecular acceptor with electron-deficient 1,3,5-triazine as the core and perylene diimides as the arms is developed as the acceptor material for efficient bulk heterojunction organic solar cells with an efficiency of 9.15%.

A π-conjugated Lewis base is introduced into perovskite solar cells, namely, indacenodithiophene end-capped with 1.1-dicyanomethylene-3-indanone (IDIC), as a multifunctional interlayer, which combines efficient trap-passivation and electron-extraction. Perovskite solar cells with IDIC layers yield higher photovoltages and photocurrents, and 45% enhanced efficiency compared with control devices without IDIC.

Air-stable doping of the n–type fullerene layer in an n–i–p planar heterojunction perovskite device is capable of enhancing device efficiency and improving device stability. Employing a (HC(NH₂)₂)_0.83Cs_0.17Pb(I_0.6Br_0.4)₃ perovskite as the photoactive layer, glass–glass laminated devices are reported, which sustain 80% of their “post burn-in” efficiency over 3400 h under full sun illumination in ambient conditions.

A series of wide-bandgap (WBG) copolymers with different alkyl side chains are synthesized. Among them, copolymer PBT1-EH with moderatly bulky side chains on the acceptor unit shows the best photovoltaic performance with power conversion efficiency over 10%. The results suggest that the alkyl side-chain engineering is an effective strategy to further tuning the optoelectronic properties of WBG copolymers.