| Perovskite solar cells(PSCs)have made remarkable achievements,which got a record energy conversion efficiency(PCE)with 25.5%.However,the commercialization of PSCs is still limited by its poor stability and high cost.Therefore,this paper focused the carbon counter electrode materials and interface modification of PSCs to achieve the purpose of cost reduction and stability enhancement.There are two main research works:(1)Development of ultra-low-cost biochar: Carbon-based perovskite solar cells(C-PSCs)perform higher stability and lower cost than traditional counterparts.However,carbon counter electrodes,such as carbon nanotubes and graphene,are still expensive.Therefore,we selected recycled biomass as raw materials to prepare biochar counter electrodes,and employed as counter electrodes of C-PSCs without hole transport materials(HTMs).Results indicated that the PCE of C-PSCs based on different biochar counter electrodes depends on the interface connection,work function,sheet resistance,crystallinity and morphology of these biochar.The comparison demonstrated that bamboo chopsticks biochar(B-CB)has the best performance,and the HTMs-free C-PSCs achieves the highest PCE of 12.82%.The device has good stability and can retain up to 87% of its initial PCE after being stored for 2000 h at room temperature.Our work provides a new way to explore low-cost biochar counter electrodes,and may accelerate the commercial application of C-PSCs.(2)Interface modification for improvement of PSCs: Interface modification can improve interface connection,passivate perovskite layer defects,and enhance device stability.In this paper,we compare perovskite heterojunction films constructed by organic sulfur ammonium salt(TMAI)and commonly used organic ammonium salt(PEAI).Results suggested that S···Pb interaction could contribute lower trap states density and longer carrier lifetime.Meanwhile,TMAI constructed 2D/3D heterostructure(TMAI-2D/3D)can realize the type-II energy level alignment(ELA)which is conducive to hole extraction and transport.However,PEAI constructed heterostructure belongs to the type-I ELA that would hinder the extraction of holes.PSCs based on TMAI-2D/3D achieved an efficiency of 20.98%,and HTMs-free C-PSCs based on TMAI-2D/3D also achieved an efficiency higher than 15%.In addition,TMAI-2D/3D also performs better thermal and moisture stability,enhancing device stability. |
