Benchmark solar to hydrogen conversion efficiency of 18.7% was achieved via photovoltaic cell- electrolyzer system without using well-known expensive IIIV-based light absorber. Comparison with previous studies indicates that this efficiency bench is impressive for using less junction (2jn instead of 3 similar to 4jn for III/V), relatively cheap perovskite and silicone solar cell, and high solar electricity to chemical efficiency (74.2%).