Executive Summary : | Organic solar cells have attracted the attention of the scientific community, especially the performance of metal halide perovskite solar cells (PSC). In the recent years, the PSCs have attained excellent power conversion efficiency (PCE) of 25.5% due to the better device performance. The power conversion efficiency in PSCs is significantly modulated by the efficient charge separation between the hole transporting material (HTM) and electron transporting material. Low-cost and highly stable ETMs such as TiO2 and SnO2 have been broadly explored with desirable electron-transporting characteristics for PSCs applications. , Hole transporting material (HTM) plays a key role to enhance the efficiency of light to electricity conversion in the perovskite solar cells. The 2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene (spiro-OMeTAD) HTM with PSCs exhibits better device performance reported to date, due to good thermal stability in ambient temperature and excellent solubility in organic solvents. However, the device fabrication of PSCs is economically less suitable due to the complex synthetic procedure and purification of spiro-OMeTAD. Additionally, the pure sublimed quality spiro- OMeTAD limits the scope of its use for the wide area of applications in PSCs. Therefore there is a need for the development of cost-effective HTMs possessing excellent hole-transporting properties. The following characteristics are essential for HTM and ETM, a) suitable lowest unoccupied molecular orbital (LUMO)/highest occupied molecular orbital (HOMO) energy levels, b) high electron mobility and conductivity, c) good solution processability, d) weak parasitic absorption, e) good stability and low cost. The HTM functions as a hole-selective contact to extract photogenerated holes and efficiently transmit holes to the counter electrode while decreasing series resistance and interfacial to reduce recombination in PSCs, leading to higher fill factor (FF) and open-circuit voltage (VOC). Therefore there is a need of new HTMs which are commercially cheap, easy to synthesize and show better device performance then the spiro-OMeTAD materials. |