A　class　of　0-dimensional/2-dimensional　(0D/2D)　nanoheterostructures　based　on　carbon　quantum　dots　(CQDs)　and　graphitic　carbon　nitride　(g-C3N4)　was　designed　as　the　signal-generation　tags　for　the　sensitive　photoelectrochemical　(PEC)　immunoassay　of　prostate-specific　antigen　(PSA)　coupling　with　the　copper　nanoclusters　(CuNCs).　Combination　of　CQDs　with　g-C3N4　promoted　the　photoexcited　electron/hole　separation　and　largely　increased　the　photocurrents　of　the　nanoheterostructures.　Initially,　a　sandwich-type　immunoreaction　was　carried　out　on　monoclonal　anti-PSA　antibody-coated　microplate　by　using　PSA　aptamer　linked　with　CuNCs　as　the　tracer.　Accompanying　the　immunocomplex,　the　carried　CuNCs　were　dissolved　under　acidic　conditions.　The　as-released　copper　ions　from　the　CuNCs　could　be　captured　onto　the　CQDs/g-C3N4　nanoheterostructures　via　the　amino-group　on　the　CQD　surface　as　well　as　the　-NHx　(x　=　1,　2,　3)　of　g-C3N4　nanosheets.　The　strong　coordination　of　the　Lewis　basic　sites　on　the　CQDs/g-C3N4　with　Cu2+　decreased　the　photocurrent　of　the　nanoheterostructures.　Under　optimal　conditions,　CQDs/g-C3N4　nanoheterostructures　displayed　good　photocurrent　responses　for　the　detection　of　PSA　within　the　dynamic　linear　range　of　0.02-100　ng　mL(-1)　and　a　limit　of　detection　(LOD)　of　5.0　pg　mL(-1).　This　method　was　also　evaluated　for　quantitative　screening　of　human　PSA　serum　specimens　by　using　the　referenced　electrochemiluminescent　enzyme-linked　immunoassay　(ECL-ELIA)　and　gave　good　matched　results　between　two　methods.　Additionally,　this　system　was　beneficial　to　explore　the　charge-separation　and　photoinduced　electron　transfer　mechanism　in　the　photoelectrochemical　sensing　protocols.