Temperature-Insensitive Efficient Inorganic Perovskite Photovoltaics by Bulk Heterojunctions

Inorganic perovskite solar cells (IPSCs) emerge as an ideal candidate for applications beyond terrestrial implementation due to their robustness. However, underlying mechanisms regarding their photovoltaic process at different temperatures remain unclear. Based on a stable absorber of CsPbI_2.85(BrCl)_0.15, considerable variation of corresponding device performance is revealed over temperature and further demonstrates a simple approach to an effective reduction of such variation. Interestingly, this absorber is found to be excitonic with poor carrier transport even at an ambient temperature of 285 K and below. With a novel device configuration of a PTB7-th/perovskite bulk heterojunction, exciton dissociation and carrier extraction is facilitated. The resultant solar cell attains a best power conversion efficiency (PCE) of 17.2% with the fill factor of ≈84%, which represents the highest-efficiency γ-phase IPSCs reported to date. Importantly, this device is less sensitive to operation temperature, wherein the PCE variation over the temperature range from 210 to 360 K is 60% suppressed compared with the reference. The approach is effectively extended to other IPSCs with different photoactive phases, which may shed light on realizing highly efficient IPSCs for specific scenarios such as polar regions, near-space, and exoplanet exploration.