Recent Progress on Mitigating Open-Circuit Voltage Loss in Inorganic CsPbX Perovskite Solar Cells.

Cesium lead halide perovskites (CsPbX, X = I or Br or their mixture) have emerged as a type of promising photovoltaic material due to their outstanding optoelectronic properties, thermal stability and low cost. Despite the great progress achieved in the corresponding photovoltaic devices, the power conversion efficiency still lags far behind their theoretical limit. Comparing with the obtained high current density and fill factor, it is of great potential for increasing the open-circuit voltage (V) value as the V loss of the CsPbX perovskite solar cells (PSCs) is still quite significant considering their wide bandgap. The primary mechanisms of V loss involve non-radiative recombination driven by bulk defects, interfacial defects, and energy level mismatching. To address the aforementioned issues, numerous strategies have been investigated including additive engineering, interface modification, charge-transport layer replacement, etc. Herein, this review summarizes the most recent work on mitigating V loss of CsPbX PSCs from three aspects, namely bulk film optimization, interface regulation, and transport layer optimization, and gives a brief outlook on how to further promote the V. With this, a guideline is provided for researchers engaging in developing CsPbX PSCs with high photovoltaic performance.