The　electron　transport　layer　(ETL)-free　perovskite　solar　cells　(PSCs)　have　gained　significant　interest　by　simplifying　the　manufacture　process　and　reducing　the　time/energy　required　for　the　fabrication　of　ETLs.　Unfortunately,　the　performance　of　these　ETL-free　PSCs　still　lags　behind　those　of　the　conventional　counterparts　due　to　the　slow　electron　extraction　and　undesired　interfacial　charge　recombination　loss　at　the　buried　interface.　In　this　work,　a　facile　and　multifunctional　biocolina　thin　layer　is　incorporated　on　the　bottom　electrodes　to　regulate　the　interface　energy　level　alignment　by　forming　an　interface　dipole　layer,　resulting　in　a　suppressed　nonradiative　recombination　and　an　improved　charge　extraction.　Furthermore,　the　biocolina　thin　layer　possess　the　capability　to　passivate　the　surface　defects　within　the　perovskite　films　while　simultaneously　facilitate　the　formation　of　perovskite　crystals.　Consequently,　a　remarkable　enhancement　in　photovoltaic　performance　is　observed　in　the　biocolina-based　ETL-free　PSCs　with　an　increase　from　15.96　%　to　an　outstanding　20.01　%.　Additionally,　the　biocolina　extends　the　stability　and　relieves　the　hysteresis　effect　through　the　interface　defect　passivation　and　inhibition　of　interface　charge　accumulation.　This　research　contributes　to　the　development　of　cost-effective,　simplified　designs　for　highly　efficient　ETL-free　PSCs　by　modifying　the　bottom　electrodes.　A　multifunctional　and　efficient　biocolina　thin　layer　is　incorporated　on　the　bottom　electrodes　to　regulate　the　interface　energy　level　alignment　and　passivate　the　surface　defects　within　the　perovskite　films　in　the　electron　transport　layer-free　perovskite　solar　cells,　achieving　a　decent　efficiency　of　20.01　%　with　an　ameliorated　J-V　hysteresis　and　environmental　stability.　image