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• Prism shaped solar still (PSS) has better heat retaining capacity than conventional solar stills (CSS). • With Lauric acid, PSS yields 2530 ml/m2 compared to CSS yield of 2360 ml/m2 with exergy efficiency of 1.01 % and 0.87 % respectively. • Black phosphorus doped Pyrex glass Quantum dot (QD) material able to absorb the large spectrum of solar radiation. • With QD and PCM, PSS yields up to 3685 ml/m2 compared to CSS yield 3040 ml/m2. • Cost analysis shows per liter of distilled water incurred INR 1.6 and 1.9 with payback period of 2.8 years and 3.2 years. The present article takes the challenge to improve solar still performance by surface coating for better energy conversion. An experimental investigation has been conducted on two solar still (SS), namely conventional solar still (CSS) facing the south direction and prism-shaped solar still (PSS) facing the east–west direction in the metrological condition of Varanasi (25.31° N), India. SS's surface solar absorptance and heat storage capacity has been modified by black phosphorus quantum dot material (BPQD) and Lauric acid. The experiments were conducted in three phases, namely SS without BPQD and PCM; SS with PCM only; and SS with BPQD and PCM on different days in nearly the same climatic conditions that showed prism-shaped solar still coated with BPQD material performed better due to its good heat retention capacity than CSS. The results showed that CSS and PSS without PCM and BPQD yield up to 1660 ml/m2 and 1830 ml/m2 with a heating efficiency of 19.72 % and 0.36 % and exergy efficiency of 25.59 %, and 1.08 %, respectively. While using PCM only, CSS and PSS yield up to 2360 ml/m2 and 2530 ml/m2 with heating efficiency of 27.84 % and 0.87 % and exergy efficiency of 35.12 % and 1.01 %, respectively. Whereas, with PCM and BPQD, SSs can produce 3040 ml/m2 and 3685 ml/m2 with exergy and heating of 1.79 % and 37.23 % for CSS, 2.20 %, and 49.30 % for PSS. Moreover, the economic analysis showed that the monetary and energy cost of distilled water incurs only INR 1.9, and INR 1.6 for each liter and INR 2.84 and 2.48 for each kWh with a payback period of 3.2 yr. and 2.8 yr. for CSS and PSS respectively. [ABSTRACT FROM AUTHOR]