Cost-effective Hole Transporting Materials For Efficient And Stable Perovskite Solar Cells

The progressive power conversion efficiencies(PCEs)of perovskite solar cells(PSCs)have attracted huge attentions from the research community.Highly efficient PSCs are often obtained with organic hole-transporting materials(HTMs)and noble metal-electrodes.These materials,however,are prohibitively expensive for scalable fabrication,and their prototypes or constituents are a factor in the instability of PSCs.Therefore,investigating cost-effective materials that can simultaneously improve the efficiency,stability and scalability of PSCs are the guidelines to promote the industrial production.The aim of this work is to replace expensive HTMs and metal-electrodes in PSCs,and scrutinize the device performance from both theoretical and experimental perspectives with cost-effective HTMs-composite.In addition to the energy levels tuning between cost-effective HTMs and perovskite layers,the performance optimization of PSCs are analyzed with-varying the thickness,defect-density and energy bandgap of perovskite layer by using 1D-software,namely:Analysis of Microelectronic and Photonic Structure(wxAMPS).Well-matched energy levels between perovskites and cost-effective HTMs revealed efficient devices due to the rapid charge extraction and low recombination rate.Ternary devices with different perovskite-layers(CH3NH3PbI3,CH3NH3PbBr3 and CH3NH3PbI2Br)are constructed to realize the best performing cell.The simulation results indicated that,due to improved photon-harvesting capability,thicker perovskite layers yield higher PCEs in relation to thinner ones.Perovskite layer with high defect-density causes a noticeable reduction in open-circuit voltage(Voc),as evidenced from current-voltage characteristic curves.However,this has very nominal impact on short-circuit current density(Jsc),particularly for the CH3NH3PbI2Br-based PSCs.Moreover,the increase in Voc,fill factor(FF),and PCE is noticed with perovskites of large energy bandgaps.Experimentally,organic-HTMs and metal-electrode are replaced by employing NiO/Carbon-spheres in planar PSCs as a composite layer.Integrating hole-accepting NiO as closely-packed nanoparticles on the core carbon spheres(CSs)improves the hole collection efficacy and minimizes losses in the recombination of charges.The small porosity of this composite inhibits the penetration of moisture and oxygen through the counter electrode,thus allowing the best device to retain 96%of the original efficiency after 1500 h at maximum power point tracking for 2000 s when exposed to ambient environment without sealing.Since organic-HTMs and noble metal electrodes are much expensive than commercially available NiO and carbon,our results establish the integration of carbon with NiO as a versatile and promising route towards upscaling the PSCs with low-cost and provide numerous options for choosing and optimizing the materials and device's layout.Furthermore,extending the applications of the NiO/CSs-composite to formation of high-quality perovskite thin-films will definitely benefit the construction of other high-performance solar cells.