Enhancing the efficiency of solar cells depends on minimizing reflection losses to boost photon absorption. In this study, we investigated the chemical etching process of pristine InP(100), (named as pris-InP(100)). Our findings demonstrate that the etching process resulted in a self-organizing V-groove microstructure, as revealed by atomic force microscopy and scanning electron microscopy. This induced V-groove microstructure resulted a significant reduction in the reflection loss. Through temporal variation in the etching process, we identified that a 5-minute etch (named as etch5-InP(100)), yielded the lowest reflectance. Additionally, radiofrequency (RF) magnetron sputtering was employed to deposit a 10 nm Nb2O5 thin film on both pris-InP (100) and etch5-InP (100) samples. The results indicated that the thin film on etch5-InP(100) exhibited significantly lower reflectance compared to pris-InP(100). Moreover, ab-initio calculations verified the stability and presence of native oxide at the interface of the Nb2O5/InP(100) heterostructure. Furthermore, dark current-voltage (I-V) characteristics indicated typical diode behaviour for both Nb2O5 thin films deposited on pris-InP(100) and etch5-InP(100). Notably, light I-V measurements revealed that the Nb2O5 thin film on etch5-InP(100) achieved a higher efficiency of 11.6 % compared to the 8.7 % efficiency of pris-InP(100). This study provides valuable insights and guidelines for the development of high-efficiency InP-based solar cells.