Efficient Nonlead Double Perovskite Solar Cell with Multiple Hole Transport Layers

Cs2AgBiBr6 having a double perovskite structure is expected to be used in nonlead and stable optoelectronic devices and has received wide attention recently. At this stage, structures of optoelectronic devices using double perovskite and hybrid perovskite are the same. And the energy band structures of double perovskite and hybrid perovskite are different, which will cause energy-level mismatch in the device with double perovskite, which in turn will seriously restrict further improvement of the device performance. A strategy to solve this problem by constructing energy-level gradients with poly(3-hexylthiophene) (P3HT)/MoO3/poly[bis(4-phenyl)(2,4,6-trimethylphenyl)-amine] (PTAA) was reported for the first time. The construction of energy-level gradient is mainly achieved by P3HT and PTAA. MoO3 plays a role in protecting the substrate (P3HT) and does not hinder hole transport because it is itself a p-type semiconductor. The champion power conversion efficiency of devices with P3HT/MoO3/PTAA is improved by more than a quarter compared to the standard devices. Moreover, in the champion device, the power conversion efficiency achieved 1.94% with a short-circuit current of 2.80 mA/cm2.