Photovoltaic cells based on organic semiconductors (OSs) have got attention due to low-cost fabrication, printability, lightweight, scalable, and easy modification compared to traditional silicon-based photovoltaics. Such materials impart specific electrical and photophysical properties that work better than silicon-based photovoltaics. However, the main problem with OSs is the power conversion efficiency and stability. Organic compounds are designed and synthesized to tackle these problems comparable to silicon-based photovoltaics. This chapter presents current advances in organic photovoltaic (OPV) devices for solar cells (SCs) employing non-fullerene acceptors and small molecule donors. For OPV materials, a broad perspective of the structure-property correlations is presented. Their photophysical properties are determined by absorption, energy levels, and carrier mobilities, among other factors. The role of OSs in photovoltaic cells is to produce excitons that dissociate into electron and hole pairs, responsible for the conduction of charge. These semiconductors work as an active layer in OPVs sandwiched between two metal electrodes: indium-tin-oxide and Al, Ca, and Mg. OSs must have diffused electronic density (π-conjugation) for photovoltaic cells for efficient optoelectronic properties. These organic compounds can be acceptors, donors, or interconnected acceptor-donor combinations with higher charge mobility than solely donors and acceptors. Different architectures of photovoltaic cells have been elaborated in this chapter, highlighting the effect of various junctions in SC devices.