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An organic solar cell (OSC), competitive with traditional one (Si-based), draws attention to future renewable energy sources due to its low-cost and continually rising efficiency. The tandem or multijunction structure undoubtedly offers an efficient way to boost the performance of OSCs. This work has explored the optical modeling of different organic photoactive materials to identify the potential materials for efficient tandem structure. The performance of double, triple, and quadruple junction tandem OSCs with suitable bandgaps has been analyzed with photoactive materials. The absorption efficiency enhances considerably using the thickness optimization of each subcell in tandem structures. Current matching in all subcells, an essential factor for efficient device operation, is taken into account while optimizing tandem structures. The quadruple design can achieve better photovoltaic performance than double or triple junction devices. The efficiency predicted from our proposed quadruple structure is ~15.45%, with a short-circuit current density, $\text{J}_{\mathrm {SC}}$ of $\sim 9$ mA/cm2 and an open-circuit voltage, $\text{V}_{\mathrm {OC}}$ of ~2.64 V. These results are one of the high-performance in terms of organic photovoltaic (OPV). Therefore, the above findings indicate that OSCs are very potential for future photovoltaic applications.

Organic solar cell draws attention because of its low cost and constantly increasing efficiency. Though having many advantages, low power conversion efficiency hinders organic photovoltaic cells from their commercialization. Tandem solar cells combine two or more single junction cells of complementary absorption band undoubtedly provide an effective means to uplift the efficiency organic solar cells. In this paper, we analyze the performance of three individual single junction organic solar cells. Single junction PCDTBT:PCBM cell shows an efficiency of 6.02% whereas PMDPP3T:PCBM and pBBTDPP2:PCBM shows efficiency of 5.99% and 3.15% respectively. Tandem cell consists of PMDPP3T:PCBM and PCDTBT:PCBM shows 10% efficiency with open-circuit voltage 1.48V and short circuit current density of 10.38 mA/cm2, Using pBBTDPP2:PCBM as a middle layer between them form a triple junction structure that offers an open-circuit voltage of 2.1 V, short circuit current density of 9.4 mA/cm2and power conversion efficiency of 12.25%, which means improved performance over the double junction structure.

An analytical model of the photocurrent-voltage characteristics has been utilized to analyze important properties of organic bulk-heterojunction solar cells, e.g., generation rate, electron current density, hole current density and the total photocurrent density. The generation rate of P3HT:PCBM based solar cell critically depends on the absorption coefficient. For measuring the electron and hole current density solution of carrier continuity equation is used in MATLAB. Then the effects of electron and hole current density on the performance of P3HT solar cells have been studied. The result of this paper demonstrate that current density due to electron plays a major role in photocurrent production while hole current density has a very little impact. Effect of electron and hole mobility variation are investigated separately which indicate that increasing electron mobility are extremely important than hole mobility to increase the power conversion efficiency of P3HT:PCBM blend. The dependence of electron and hole current densities as a function of the blend thickness is also analyzed.

Tandem solar cell provides an effective way to improve power conversion efficiency of organic solar cell by combining two or more organic solar cells. Each cell has different absorption maximum and width so it provides the amenities of using the photon energy more effectively. Due to the limited absorption band of organic materials, single junction organic solar cells suffer from low efficiency. Here, we demonstrate the performance of single layer devices based on the solution of carrier continuity equation in MATLAB. Polymers P3HT:PCBM, pBBTDPP2:PCBM and PCDTBT:PCBM provide power conversion efficiency of 3%, 3.15% and 6.2% respectively. Hence series connected tandem cell P3HT:PCBM as front cell and pBBTDPP2:PCBM as rear cell is designed to achieve higher efficiency where the proposed model gives the power conversion efficiency of 6%. A major back through came when the front cell is replaced by PCDTBT:PCBM solar cell in the device configuration which provides the power conversion efficiency of 8.8%, till now the maximum efficiency for organic solar cell.