Further minimizing the defect state density in the semiconducting absorber is vital to boost the power conversion efficiency of solar cells approaching Shockley-Queisser limit. However, it lacks a general strategy to control the precursor chemistry for defects density reduction in the family of iodine based perovskite. Here the alkaline environment in precursor solution is carefully investigated as an effective parameter to suppress the incident iodine and affects the crystallization kinetics during film fabrication, via rationale adjustment of the alkalinity of additives. Especially, a ‘residual free’ weak alkaline is proposed not only to shrink the bandgap of the absorber by modulating the stoichiometry of organic cation, but also to improve the open circuit voltage in the resultant device. Consequently, the certified efficiency of 20.87% (Newport) is achieved with one of the smallest voltage deficits of 413 mV in the planar heterojunction perovskite solar cell.

Non-fullerene polymer solar cells (PSCs) attract more attention due to the constantly refreshed power conversion efficiency (PCE) based on the versatile non-fullerene acceptors. In this work, PCEs of 10.51% and 11.02% were obtained for two kinds of non-fullerene PSC with IDT6CN-M or ITCPTC as the acceptor and PBDB-T as the donor. ITCPTC has a relatively narrow bandgap and a high absorption coefficient compared with IDT6CN-M, which explains well the relatively large short-circuit current density of 17.44 mA cm⁻² for the ITCPTC based binary PSCs. Meanwhile, the IDT6CN-M based binary PSCs exhibit a relatively high fill factor (FF) of 75.3% and an open-circuit voltage of 0.915 V. A PCE of 11.92% and a FF of 76.5% were achieved for the ternary PSCs with 60 wt% ITCPTC content in the acceptors, which should be attributed to the enhanced photon harvesting and their good compatibility for a synergistic improvement of exciton utilization and charge transport in the ternary active layers. The FF of 76.5% is among the top values of ternary non-fullerene PSCs.

A new approach for the synthesis of infinite Ti–O rod-based MOFs with superior photocatalytic H₂ evolution performances was developed.