Lifecycle assessments suggest preventing halogenated solvents or solvent additives for environmentally friendly polymer solar cells. Thus, the active layers of polymer:fullerene bulk heterojunction solar cells based on poly{[4,8‐bis‐(2‐ethyl‐hexyl‐thiophene‐5‐yl)‐benzo[1,2‐b:4,5‐b0]dithiophene‐2,6‐diyl]‐alt‐[2‐(20‐ethyl‐hexanoyl)‐thieno[3,4‐b]thiophen‐4,6‐diyl]} (PBDTTT‐CT) and the fullerene derivative [6,6]‐phenyl‐C70‐butyric acid methyl ester (PC70BM) are cast from m‐xylene solutions. Ortho‐vanilline is used as a nonhazardous and nontoxic solvent additive. Completed photovoltaic devices are subjected to accelerated laboratory weathering tests. Photovoltaic parameters are periodically obtained from current–voltage recordings of the solar cells twice an hour under well‐defined aging conditions following the International Summit on Organic Photovoltaic Stability (ISOS) protocols. An analysis of aging kinetics reveals the superposition of two individual degradation mechanisms, of which one is assigned to continued intermixing and the other one to the formation of a blocking layer by interfacial segregation.

<p class="0abstract">This paper is an effort to analyze the performance and also increase the efficiency of InGaN/GaN solar cell. InGaN/GaN solar cell contains p and n-type layer of GaN and intrinsic layer of InGaN. The proposed structure of solar cell also contains front TCO, back TCO and back reflector. Performance of the designed solar cell was checked based on electric field, current density and electric potential generated in the designed cell. J-V curve is the most important factor to analyze the performance of the solar cell. Power conversion efficiency and fill factors have been calculated from this graph. According to the analysis of the simulation results efficiency of the designed solar cell was 12.91%. At the end, this thesis is about designing successfully with an efficient InGaN/GaN solar cell for further use in solar applications.</p>