Correlation between Urbach energy (EU) and open-circuit voltage deficit (VOC,def) among conventional as well as emerging thin-film solar cells, i.e. Cu(In,Ga)Se2 (CIGSe), Cu(In,Ga)(S,Se)2 (CIGSSe), Cu2SnS3 (CTS), Cu2Sn1-xGexS3 (CTGS), SnS, Cu2ZnSnSxSe4-x (CZTSSe), perovskite (PVK), Cu(In,Ga)S2 (CIGS), and CdTe thin-film solar cells, is examined. The EU is estimated from an exponential tail in a long-wavelength edge of an external quantum efficiency. It is determined that the relation between short-circuit current density (JSC) and EU is not clearly shown because the JSC is primarily influenced by the bandgap of the thin-film absorbers. On the other hand, EU demonstrates a close relation with VOC,def, where the reduction of the EU leads to the decrease in the VOC,def, implying that the EU can be used as an indicator of the absorber quality. The EU of over 20 meV, observed in the CIGS, CTS, CTGS, SnS, and CZTSSe solar cells, gives rise to the high VOC,def and the low conversion efficiency (η) values. The EU of below 20 meV, seen in the CIGSe, CIGSSe, PVK, and CdTe solar cells, leads to the low VOC,def and high η values. Ultimately, the thin-film absorbers with the EU values of below 20 meV, which is lower than thermal energy under room temperature, is of vital to realize high photovoltaic performances.